Field of the Invention
Various embodiments relate to a coil arrangement for generating a rotating electromagnetic field, and to locating systems for determining a position of an identification transmitter. Such locating systems may include inventive coil arrangements.
Description of the Background Art
Techniques are known that permit locating, i.e. determining a position, e.g. of identification transmitters. One example of an identification transmitter would be for instance a key for a motor vehicle. Thus techniques are known that permit the position of the key in the vicinity of the motor vehicle to be determined in order to attain access control to the motor vehicle. Conventional techniques are typically based on a measurement of a field strength of an electromagnetic field transmitted by a central transmitter. Since the field strength decreases as distances to the transmitter increase (damping or decay of the field strength), it is possible to use a receiver antenna in the key to deduce a position relative to the transmitter from a measurement of the field strength.
However, such techniques may have limited precision in determining the position of the identification transmitter, e.g. due to limited precision when measuring the field strength. Typical precision in determining positions with known systems is e.g. 20 cm-approx. 2 m. Moreover, systemic corruptions may occur; in particular the decrease in the field strength of the electromagnetic field may be disturbed, for example, due to magnetic objects such as for instance the vehicle body, etc., so that determining the position of the identification transmitter may be suffer from a certain systemic error. Such cases may make it necessary to perform a one-time manual measurement of the decay of the field strength in and around the motor vehicle for calibrating position determination. Such a manual measurement may be time-consuming and there may be associated costs. The calibration itself may also be the source of errors. Moreover, it may not be possible also to perform the position determination inside the motor vehicle, or it may only be possible with limitations. This may be the case because the decay of the field strength may be profoundly disturbed in the interior of the motor vehicle by a wide variety of components.
The foregoing described disadvantageous effects of the prior art with respect to the techniques for position determination itself. However, disadvantageous effects may also occur with respect to the system architecture of related devices, as shall be illustrated in the following. For instance, previously known locating systems for position determination typically have a central control device that is connected by means of power supply lines to the individual transmitters that transmit the electromagnetic field. The provision of these supply lines to the plurality of transmitters, typically three to five transmitters, may claim installation space in the motor vehicle, however, and render necessary time-consuming and expensive wiring to e.g. two core or four core cable lines. Moreover, such systems frequently have only limited modularity because it is not possible to operate the system functionally with a lower or greater number of transmitters with nothing further—it is therefore not possible to provide different equipment variants, or it is only possible to a limited degree. In addition, the system may be comparatively susceptible to faults because a failure of or disturbance to the central control device frequently may result in complete failure of the system.
For the reasons provided in the foregoing there is a need for improved techniques for determining a position of a receiver. In particular there is a need for locating systems that make possible particularly precise position determination inside and outside of the motor vehicle and simultaneously have low susceptibility to faults and a simple and cost-effective system architecture.